Is adjacent lobe invasion an T category upgrade factor for resected non-small cell lung cancer ≤ 5cm?

Abstract

Controversy exists with regard to the T category of non-small cell lung cancer (NSCLC) with adjacent lobe invasion (ALI), and dispute arises on assigning this subset into T2 or T3 category. We evaluated the effect of ALI on the survival of resected NSCLC ≤ 5cm, with purpose of determining the most appropriate T category for this population. The entire cohort was divided into three subgroups (ALI group, T2 group and T3 group). Kaplan-Meier with log-rank method was carried out to compare overall survival (OS) differences. Propensity score matching (PSM) was performed to minimize bias. A total of 12,564 eligible NSCLC cases (ALI group: 114 cases; T2 group: 10,046 cases; T3 group: 2404 cases) were included in this study. The incidence of ALI was about 0.9%. Before PSM, survival analyses demonstrated that no significant OS differences were observed between ALI group and T2 group, and between ALI group and T3 group, neither in the entire cohort analysis nor in the subgroup analysis. After PSM, there were 102 pairs and 98 pairs in the ALI and T2 matching group and ALI and T3 matching group, respectively. In the matched cohorts, survival curves showed that the OS of ALI group was comparable to that of T2 group (P = 0.950), but superior to that of T3 group (P = 0.012). The current study proposed that NSCLC with ALI ≤ 5cm should be still categorized as T2 category, which could improve staging accuracy.